1. Field of the Invention
This invention relates to devices for positioning a plug for filling a hole to repair a rigid sheet, such as a pane of glass.
2. Description of the Prior Art
It can be prohibitively expensive to replace entire panes of plate glass each time such a pane is cracked. Many methods have been tried to repair cracks, in order to avoid this expense. One technique involves removing a piece of glass around the crack by cutting a circular hole through the pane. A glass plug, slightly smaller in dimension than the hole, is inserted in the hole. The circular gap between the plug and the pane of glass is then filled with a bonding material such as plastic resin. This technique is generally discussed in U.S. Pat. No. 3,986,913 to Walz, issued Apr. 24, 1975.
A subsequent patent to Walz, U.S. Pat. No. 4,073,094, issued Feb. 14, 1978, discloses apparatus for cutting the hole in the pane.
In order to perform a satisfactory repair, the surface of the glass plug must be exactly in the plane of the surface of the pane of glass being repaired. Any deviation between the plane of the surface of the plug and the plane of the pane of glass results in distortion and reflections which make the repair immediately visible and esthetically unappealing. The essential characteristic required in positioning the plug in the hole before bonding is the ability to align the plug properly to avoid the negative characteristics which result from the plug lying out of the plane of the pane of glass.
One alignment tool is disclosed in U.S. Pat. No. 4,208,229 to Giardini, issued June 17, 1980. FIGS. 3 and 4 show a disk 134 which rests against the pane of glass and the plug 130. Plug 130 is mounted to disk 134 by pressure-sensitive adhesive film. The disk is then mounted over the opening in the pane of glass, so that the glass plug and the pressure-sensitive adhesive film are aligned in the opening, with the adhesive film generally in the plane of the surface of the glass pane.